1. Field of the Invention
The present invention relates to a connector, in particular intended for use on a tension leg platform, comprising a male part and a female part, in which the male part is intended for entering in the female part and are able to make engagement with each other without the need for any of the parts to rotate in respect of the other.
2. Description of the Related Art
During exploration of oil and gas resources in deep waters, tension leg platforms, or TLP, are more frequently used. Such a platform comprises a floating installation moored to the seabed by means of vertical mooring stays called tension legs. These tension legs do substantially suppress three of the six degrees of freedom of a floating vessel. A tension leg platform can not heave, pitch or roll, but can surge, sway and yaw. Tension legs feature connectors, located at the bottom and top of each tension leg. The connectors have to transmit the mooring loads in the tension legs while permitting an angular motion in relation with surging, swaying and yawing.
The present invention is directed toward a new design of the bottom connector part of the tension leg that connects the tension leg to a connector part in a base structure on the seabed.
The functions of such a bottom connector are that angular motion is allowed, the connector is able to transmit the mooring forces to the sea bed base structure, and the connector is not permanently connected to the tension leg.
A number of designs for this type of bottom connector are previously known. One design requires that the entire tension leg needs to be rotated in order to engage a locking mechanism in the connector.
An early version of a bottom connector design made use of a system having spring biased collect fingers requiring that the tension leg, be landed on the bottom of the sea bed connector having a predetermined load in order to activate the locking mechanism.
A design recently utilised in the North Sea requires no locking mechanism when the bottom connector is entered into the base structure on the sea bed by means of lateral entrance by a slot in the side wall of the load supporting structure.
One design that is often used in the Mexican Gulf is a variant of the concept comprising the rotatable lock. This design, however, does not require that the entire tension leg be rotated. The male part of the connector has a rotatable ring that is rotated in that the male part is lowered into the female part of the connector and then elevated. The female part has a system with lugs and slots, which carries the locking mechanism into correct orientation. A lowering and elevating the male part of the connector a second time rotates system again, allowing disconnections.
The present invention improves the existing designs by enabling a vertical entering and eliminates at the same time the need to rotate the tension leg or any part thereof. Further, the need of a vertical locking force is avoided. Also the need for a system having slots and lugs on the internal wall of the female part is ceased.
The male part may be entered vertically into the female part. The male part locks to the female part automatically when it is entered. The connector does not need to be rotated in order to engage properly. The locking is performed by means of the net weight of the tension leg. When the male part is in engagement in the female part, the connector can only be disconnected again by use of external tools. Thus the design becomes fail-safe since, when it is loaded or strained, the locking can not be released.
In a preferred embodiment, the connector comprises a female part and a male part. The female part comprises an abutment ring having a continuously downward facing internal abutment shoulder; the male part has a discontinuous segmented ring, wherein each individual ring segment is independently movable, both axially and radially. The segmented ring lies slideably against a mandrel.
Further, the upper portion of the female part may have a funnel form for axial and radially inward guiding of the segmented ring on the male part during the entering thereof into the female part. Advantageously the abutment shoulder can also be bevelled downwards and outwardly to form a wedge surface. The male part may include an entering portion that is tapered downwardly for entering into the female part. Further, each segment may remain in loose connection with a continuous annular body via guiding bolts or stays. The mandrel on the male part can be tapered upwardly, or conical, and form a wedge surface. Each segment may have an outwardly facing surface which corresponds with the downwardly facing surface of the abutment shoulder, and an inwardly facing surface which corresponds with the abutment surface of the mandrel, said two segment surfaces converging upwardly in order to form a wedge.